Nickel-eating bacteria blamed for the world's worst extinction

Nickel-eating bacteria may have worsened the world's worst mass die-off by producing huge amounts of methane, a new study suggests.

The study is the latest attempt to explain how most of the world's ocean species died off in just a few hundred thousand years at the end of the Permian era, about 250 million years ago. The researchers presented their findings Tuesday here at the annual meeting of the American Geophysical Union.

The study proposes that a series of steps caused the mass extinction, but that bacteria played a key role. First, massive volcanic activity in Siberia released nickel into the atmosphere, which somehow reached the ocean. As a result, populations of ocean-dwelling bacteria that use nickel in their metabolic pathway exploded, releasing huge amounts of methane into the atmosphere and depleting ocean oxygen levels as a byproduct of that metabolism. Because methane is a greenhouse gas, the catastrophic gas release trapped heat in the atmosphere and caused the mass extinction by making the climate uninhabitable.